Islamabad, Pakistan — Once again, anger is threatening the already volatile US-Pakistani relationship after the deadly cross-border attack – the worst friendly fire incident since the start of the 10-year war in Afghanistan – by NATO on Pakistani forces late last month.

Adding bite to the rhetoric, Islam­abad boycotted the Bonn Con­ference in Germany, Dec. 5 on the future of Afghanistan, which is part of a US search for a graceful exit. Also this week Pakistan pulled some troops from posts along the border with Afghanistan.

Yet behind the headlines, the two have such strong mutual interests that a severance in US-Pakistani ties is unlikely. Pakistan relies heavily on the aid and connections it has won through its relationship with the US, which keep it from international isolation, and America still needs Pakistan, a nuclear power and the country with the second-largest Muslim population in the world, for strategic reasons long after troops draw down in Afghanistan.

To be sure, the deaths of 24 Pakistani soldiers have inflamed public opinion against the US, in a year when a CIA contractor killed two civilians on the streets of Lahore and America conducted a unilateral raid to kill Osama bin Laden on Pakistani soil. Polls put Pakistanis with a favorable opinion of the US at around 12 percent of the population, and there's little love lost on the other side.

Making matters worse, public distrust has reached such levels that right now overt moves toward reconciliation aren't possible for either side.

"Neither the United States nor Pakistan can be seen to their public as giving space where it's not deserved," says Mosharraf Zaidi, a political analyst.

In Pakistan, anger has manifested in a cut to the NATO supply line, street protests, and the yanking of foreign news channels off the air.

Such fury has been compounded by President Obama's refusal to make a videotaped apology for the airstrike incident, having already expressed regret through the White House press secretary.

On Dec. 1, the US hit back with its own version of events, as officials told The Wall Street Journal that Pakistan had given the green light on the attack, unaware that their own troops were in the area.

US aid fatigue

On the US side, pressure is mounting – particularly on Capitol Hill – to make deeper cuts to the $1.5 billion in aid the "unreliable ally" receives each year. A Western diplomat in Islamabad said that the US embassy fears Pakistan may soon be willing to force the issue itself by refusing to accept American aid – a fresh diplomatic blow.

Why then does the US continue to engage with Pakistan?

For a start, there is that matter of the NATO supply line, vital to its efforts for a successful outcome in Afghanistan. Despite shifting some of that route through the friendlier Central Asian states in recent years, the Pakistani route that runs from the port city of Karachi across the Western border at Torkham still accounts for almost half the multinational force's provisions.

Then there is the disputed US presence at Shamsi airbase in Pakistan's Balochistan Province, where the US launches its controversial drone program – key in the battle against Al Qaeda and Taliban militants along the Afghan-Pakistani border. Though Pakistan officially ordered the US to vacate the bases following the NATO airstrike, the US denies having a presence there.

For Pakistan, US aid does not matter as much as the connections America brings with it – namely the International Monetary Fund and the World Bank, upon whose loans Pakistan's economy is dependent – coupled with the overwhelming desire to avoid international isolation. Despite the hostile rhetoric, that desire trumps anti-American sentiments within the Pakistani Army, according to Amir Rana, director of the Pakistan Institute for Peace Studies, a think tank.

"The people who matter in the military establishment know that losing America means losing 70 percent of the world," he says.

And then there are the two countries' mutual friends in the Muslim world: Saudi Arabia and Turkey, who would step up as go-betweens during any breach in ties between the US and Pakistan, says Mr. Zaidi, the analyst.

So what can we expect for the future of US-Pakistani ties?

Both countries share short-term objectives for a peaceful and stable Afghanistan, which will allow the Obama administration to show serious progress in time for next year's elections, according to Ayesha Siddiqa, author of "Military Inc.," a book on Pakistan's military-industrial complex.

Indeed, NATO and Pakistani troops resumed some level of cooperation by working together to prevent another cross-border incident, The Associated Press reported in late November.

'Strategic divergence'

In the long run, however, Ms. Siddiqa sees "strategic divergence." She says, "Pakistan views Afghanistan and Central Asia – particularly Af­ghan­istan – as its own backwater. It's a Pakistani version of the Monroe Doctrine," referring to a US policy from the 1820s that declared Latin America off limits to Europe.

That's an analogy the US doesn't share, says Siddiqa, who foresees a toned-down, bare-minimum relationship that emphasizes the security-related goals the two countries share, minus the pretense of a close friendship. "They'll drift apart. There will be greater crises, greater tensions, another problem will come along.

"None of this means Pakistan will cease to have ties with the US," she adds. "We'll remain engaged tactically, but reduce our dependence."